1. Field of the Invention
In general, the present invention relates to gauges used to measure the angle between converging or diverging surfaces. More particularly, the present invention relates to hand held tools used in carpentry that are used to measure angles so that various carpentry tools can be set to the measured angles and produce accurate mitered cuts.
2. Description of the Prior Art
Carpenters are often required to join pieces of wood at corners. When joining pieces of wood at an angle, the ends of the pieces of the wood must be mitered in order to match the angle of the corner and produce an aesthetically pleasing joint. When corners meet at a right angle, the mitering process is relatively simple. However, when pieces of wood are joined at an acute angle or at an obtuse angle, the task of creating a proper joint becomes more complex.
In carpentry, the first step needed to create a proper joint between converging surfaces is to measure the angle between the converging surfaces. Once the angle is known, the measured angle is bisected and the carpenter""s mitering tools are set to the value of the bisected angle. Both converging pieces of wood are then cut to the bisected angle. When the two pieces of wood are joined, the pieces of wood meet at an angle equal to the measured angle and a proper joint is created.
The prior art is replete with various different types of gauges that are used to measure the angle between converging or diverging surfaces. Early carpentry tools used to measure angles had two articulated arms that were joined to a common pivot point. The arms were rotated to match the angle of the surface being measured. A protractor was then used to measure the angle between the arms, so a carpenter new at what angle to set his tools. Such prior art gauging tools are exemplified by U.S. Pat. No. 1,135,743 to Walker, entitled Combination Tool.
In the years that followed, gauging tools have been improved in that a protractor has been incorporated into the gauge. As such, a carpenter can read an angle directly from the gauge rather than having to use both a gauge and a protractor. Such prior art gauges are exemplified by U.S. Pat. No. 4,060,900 to Greenwood, entitled Angle Measuring Device and U.S. Pat. No. 4,535,542 to Liu, entitled Vernier Gauge.
A problem associated with the use of such prior art angle gauges is tolerance error. When a carpenter measures an angle, the measured angle contains some error that corresponds to the quality of the gauge being used and the care taken by the carpenter when measuring the angle. Additionally, the measured angle is then divided in half, which often produces rounding errors. The calculated value of the bisected angle is then used to set the carpenter""s mitering tools. The tools often do not have highly accurate angle setting devices and the mitering tool may have a tolerance error of xc2x12 degrees. The combined errors created by the gauge, the mitering tool and rounding errors often cause the resulting joint to be less than perfect. As such, a carpenter must repeat the process or subject the wood to a secondary cutting process until a joint of satisfactory quality is obtained.
If a carpenter is making high quality furniture, picture frames or trim where a very small margin of error is acceptable, the carpenter typically uses very high quality gauges and mitering tools. Such high quality tools do produce accurate cuts. However, such tools are very expensive and are not economically practical to many professional and amateur carpenters.
A need therefore exists for a device and method for accurately gauging an angle and setting inexpensive mitering tools to the measured angle, thereby enabling accurate miters to be dependably produced from common equipment. This need is met by the present invention as it is described and claimed below.
The present invention is a gauge device and the associated method of using the gauge device to set the cut angles of a carpenter""s mitering tools. The device includes a handle that has a longitudinal axis. A first arm is pivotably connected to the handle. The first arm has at least one straight edge. The straight edge of the first arm creates a first angle with the longitudinal axis of the handle. A second arm is also pivotably connected to the handle. The second arm has a straight edge that creates a second angle with the longitudinal axis of the handle. A spanning mechanism is provided that selectively maintains symmetry between the first angle of the first arm and the second angle of the second arm. The second arm is selectively detachable from the spanning mechanism and is movable to a retracted position. The second arm is retracted when the gauge device is used to set the cutting angle on a mitering tool.